Study on the applications of photoreactive materials for flexible display device

Abstract

There has been significant interest in the development of a flexible display technology. Flexible flat panel displays offer many potential advantages, such as reduced thickness and weight, improved durability, and the ability to flex, curve, conform, roll, and fold a display for extreme portability, high-throughput manufac-turing, and ultimate engineering design freedom. To enable a flexible flat panel display, a flexible substrate must be used to replace conventional glass substrates, which can be either thin metal or plastic. Liquid crystal displays utilize the optical properties of a specific state of liquid crystals in the presence or absence of external electric field. A liquid crystal display using plastic substrates is the most promising device for the flexible display since the relevant technologies have been well established in recent years. The liquid crystal alignment layers are essential for uniaxial control of the direction of liquid crystals in liquid crystal displays. Among various methods to align liquid crystals, the rubbing method has been widely used for the generation of optical anisotropy due to simple and rapid process. However, high temperature process of rub-bing method is not suitable for plastic substrate-based displays. Therefore, several liquid crystal alignment techniques have developed as alternatives to the rubbing process typically including photoalignment, imprint-ing, and oblique evaporation. In particular, photoalignment based on the generation of an anisotropic distribution of the photoreactive moieties by irradiation of polarized light has gained substantial attention, as it can be carried out under low temperature. Firstly, I demonstrated a contact-free method of designing flexible liquid crystal displays with photoalignment layers having spacers on a plastic substrate for good liquid crystal orientation properties in the bending condition (Chapter 2). Additionally, I proposed the fabrication method of modified photoalignm...